Saliou Diouf | Universite Cheikh Anta Diop De Dakar (original) (raw)

Papers by Saliou Diouf

Journal of Minerals and Materials Characterization and Engineering

The disposal of waste has become an environmental issue due to the limited available landfilling ... more The disposal of waste has become an environmental issue due to the limited available landfilling space. This paper aims to compare the characteristics of hydrated lime with fine sewage sludge ash (FSSA) and coal fly ash (CFA). Multiple techniques, X-ray fluorescence (XRF), X-ray diffraction (XRD), the Fourier transform infrared (FTIR), compressive strengths, thermophysical properties, and setting time were used to assess the physicochemical characteristics of the lime-based materials. X-ray fluorescence and X-ray diffraction were used to determine the chemical composition and phases of ashes, lime and binders. The results showed that the chemical composition of ashes is similar to that of cement. Besides glass, the main minerals identified in CFA and FSSA are quartz (SiO 2) and anhydrite (CaSO 4). Moreover, calcium aluminium oxide (Ca 3 Al 2 O 6) was detected for CFA and phosphorus calcium silicate (Ca 2 SiO 4-Ca 3 (PO 4) 2) for FSSA and minor phases were detected for both. FTIR measurements were carried out to characterize the inorganics components of different samples. Compressive strengths of mortars with different formulations have shown that both have a long-term positive effect which might be related to a pozzolanic activity. For the CFA the L 3 binder consisting of 60% of coal fly ash and 40% lime has a higher compressive strength than the others while for the FSSA the L 4 binder consisting of 80% fine ash and 20% lime has a higher compressive strength than the others. Both binders setting start times are greater than that of cement but shorter than that of lime. The study of the thermophysical properties of binders shows that they have a higher thermal resistance than cement mortar. Moreover, binders heat up less quickly because of their low effusivity compared to cement. Lime-based ma

Advances in Materials, 2021

Recycling of wastes and their by-products is attracting increasing interest worldwide because of ... more Recycling of wastes and their by-products is attracting increasing interest worldwide because of the high environmental impact in the cement, concrete and other industries. This work deals with the study of the physico-chemical characteristics of binders based on sewage sludge ashes and lime. In a first step, we used X-ray fluorescence to determine the chemical composition of ash, lime and binders. This allowed us to see that the chemical composition of sewage sludge ash is similar to that of cement. We then used X-ray diffraction to identify the main mineralogical phases in the samples. Compressive strengths of mortars containing 20%, 40%, 60% and 80% of SSA showed that SSA has a long-term positive effect which might be related to a slight pozzolanic activity. The L 4 binder consisting of 80% fine ash and 20% lime has a higher compressive strength than the others. The binder setting start time is greater than that of cement but shorter than that of lime. The study of the thermophysical properties of the L 4 binder shows that it has a higher thermal resistance than cement and clay mortars. Moreover, it heats up less quickly because of its low effusivity compared to the latter two. This analysis highlighted the principal characteristics that must be taken into account to use SSA correctly in lime-based materials.

The densification behaviour, microstructural changes and hardness characteristics during spark pl... more The densification behaviour, microstructural changes and hardness characteristics during spark plasma sintering of CP-Ti reinforced with TiC, TiN, TiCN and TiB2 were investigated. Commercially pure Ti powders were dry mixed with varied amounts (2.5 and 5 wt. %) of the ceramic additives using a T2F Turbula mixer for 5 h and at a speed of 49 rpm. The blended composite powders were then sintered using spark plasma sintering system (model HHPD-25 from FCT Germany) at a heating rate of 100 o C min-1 , dwell time of 5 min and sintering temperature of 950ºC. The sintering of CP-Ti was used as a base study to select the proper spark plasma sintering temperature for full density. Densification was monitored through analysis of the recorded punch displacement and the measured density of the sintered samples using Archimedes method. High densities ranging from 97.8% for 5% TiB2 addition to 99.6% for 5% TiCN addition were achieved at a relatively low temperature of 950°C. Microstructural analys...

Geomaterials, 2022

Coal fly ash is considered an industrial by-product derived from coal combustion in thermal power... more Coal fly ash is considered an industrial by-product derived from coal combustion in thermal power plant. It is one of the most complex anthropogenic materials. Its improper disposal has become an environmental concern and resulted in a waste of recoverable resources. The aim of this paper is to study the physico-chemical characteristics of binders based on coal fly ash and lime in order to develop an eco-cement. The various characterization tests carried out are X-ray fluorescence, X-ray diffraction, compressive strengths, thermophysical properties and setting time. X-ray fluorescence and X-ray diffraction were used to determine the chemical composition and phases of fly ash, lime and binders. This allowed us to see that the chemical composition of fly ash is similar to that of cement. Compressive strengths of mortars containing 20%, 40%, 60% and 80% of fly ash have shown that fly ash has a long-term positive effect which might be related to a pozzolanic activity. The L 3 binder consisting of 60% of coal fly ash and 40% lime has a higher compressive strength than the others. The binder setting start time is greater than that of cement but shorter than that of lime. The study of the thermophysical properties of the L 3 binder shows that it has a higher thermal resistance than cement mortar. Moreover, it heats up less quickly because of its low effusivity compared to that of the latter. This analysis highlighted the principal characteristics that must be taken into account to use coal fly correctly in lime-based materials.

Journal of Civil, Construction and Environmental Engineering

New environmental challenges and research opportunities arise on the use of solid wastes as well ... more New environmental challenges and research opportunities arise on the use of solid wastes as well as their basic properties. In fact, recycling of these wastes and their by-products is attracting increasing interest worldwide because of the high environmental impact in the cement, concrete and other industries. Two types (type1: Fa100 and type 2: Ba100) of sludge ashes from the sludge waste center of Camberene (Senegal) were combined with different proportions of lime to assess their potential use in civil engineering. XRF, optical microscopy and spectroscopy were used to characterize the samples. The following major elements are present in the ashes: SiO 2 , Al 2 O 3 , Fe 2 O 3 , CaO, P 2 O 5. For the minor elements their concentration are very important in type 1 compared to those in type 2. These ashes have similar composition with cement except for CaO. The measurement of absorbance on the ashes shows a clear difference in optical absorption between samples. The lime pellet transmits more compared to Ba100 and Fa100 pellets. The materials obtained by mixing ash with lime in various proportions have a lower optical transmission with respect to lime and ash taken separately. Thus, the designed materials transmit less light which suggests an improved thermal isolation. The studied ashes suggest that they are not dangerous based on the Annex III of (criterion H14 of Directive 91 / 689 / EEC).

Journal of Alloys and Compounds

Selective laser sintering (SLS) was adopted to rapidly prepare silica-based ceramic shell for sup... more Selective laser sintering (SLS) was adopted to rapidly prepare silica-based ceramic shell for superalloy turbine blade, and combined with high-temperature sintering process to further improve the mechanical properties of ceramic shell. The effects of different sintering temperatures (1450~1600 ℃) on the flexural strength of alumina-based ceramic shells were investigated. The phase constitution and fracture morphology of alumina-based ceramic shell molds were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that ceramic shell with excellent mechanical properties can be obtained by SLS+high-temperature sintering quickly and effectively. As sintering temperature increases from 1450 ℃ to 1600 ℃, flexural strength of ceramic shell at room temperature increases, and reaches 38.03 MPa at 1600 ℃. Columnar mullite phase is the main strengthening phase, with the increase of sintering temperature, the content of mullite phase in the shell increases, the content of quartz phase decreases, and the content of cristobalite phase increases first and then decreases. The crack propagation form changes from slow expansion to rapid expansion and causes transient fracture. The fracture changes from a tearing shape to a flush small section, and appear the intergranular and transgranular fracture mode, the crack is tended to expand to the mullite particles.

Journal of Alloys and Compounds, 2015

Powder Metallurgy, 2012

ABSTRACT The effect of particle size on the densification mechanism of as atomised copper powder ... more ABSTRACT The effect of particle size on the densification mechanism of as atomised copper powder during spark plasma sintering was investigated. In the temperature range 600-700 degrees C and pressure range 20-30 MPa, consolidation of the powders is given by rearrangement, deformation, neck formation and minimal growth. Deformation and neck formation are enhanced by an increase in the particle size, since the current flow in the contact areas increases with the particle size. The actual pressure in the contact area, instead, does not change with the particle size. The extremely high and localised temperature on the contact points between particles leads to melting, giving rise to neck formation. The high temperature decreases towards the centre of the particle, allowing thermal softening and increasing the deformability of the particle core.

Powder Metallurgy, 2013

Abstract The densification and sintering behaviour of a cryomilled copper powder (grain size of 1... more Abstract The densification and sintering behaviour of a cryomilled copper powder (grain size of 17±2 nm and dislocation density of 6·26±0·04×1016 m−2) were investigated and compared to those of an atomised copper powder with the same mean particle size in order to highlight the effect of the nanostructure on spark plasma sintering (SPS). Oxygen and nitrogen contamination of the cryomilled powder gives rise to extensive degassing during SPS up to 400°C. The cryomilled powder is more resistant to plastic deformation than the atomised one, but the huge density of dislocations and grain boundary activates sintering at low temperature. Densification is therefore promoted by deformation in the atomised powder and by sintering shrinkage in the cryomilled one. As a consequence, in the SPS conditions investigated, the atomised specimen is densified but not sintered, while the cryomilled one is effectively sintered and consequently densified.

$Research paper thumbnail of A fractographic and microstructural analysis of the neck regions of coarse copper particles consolidated by spark plasma sintering$

Materials Letters, 2013

Abstract The effect of the surface overheating occurring during spark plasma sintering was invest... more Abstract The effect of the surface overheating occurring during spark plasma sintering was investigated by means of a fractographic and microstructural analysis of specimens produced with large copper particles. The overheated layer is quite thick and its microstructure is clearly different from that of the bulk of the particles, comprising coarse columnar grains oriented along the radial direction. Such a microstructure indicates that the temperature at the surface of the particles may effectively overcome the melting point of the material, leading to fast melting and re-solidification.

International Journal of Refractory Metals and Hard Materials, 2016

Mixed 93W-4.9Ni-2.1Fe powders were sintered via the spark plasma sintering (SPS) and hybrid spark... more Mixed 93W-4.9Ni-2.1Fe powders were sintered via the spark plasma sintering (SPS) and hybrid spark plasma sintering (HSPS) techniques with 30 mm and 60 mm samples in both conditions. After SPS and HSPS, the 30 mm and 60 mm alloys (except 60mm-SPS) had a relative density (>99.2%) close to the theoretical density. Phase, microstructure and mechanical properties evolution of W-Ni-Fe alloy during SPS and HSPS were studied. The microstructural evolution of the 60 mm alloys varied from the edge of the sample to the core of the sample. Results show that the grain size and the hardness vary considerable from the edge to the core of sintered sample of 60 mm sintered using conventional SPS compared to hybrid SPS. Similarly, the hardness also increased from the edge to the core. The 60 mm-HSPS alloy exhibit improved bending strength than the 60 mm-SPS, 1115 MPa and 920 MPa respectively, former being similar to the 30 mm-SPS and HSPS alloys. The intergranular fracture along the W/W grain boundary is the main fracture modes of W-Ni-Fe, however in the 60 mm-SPS alloy peeling of the grains was also observed which diminished the properties. The mechanical properties of SPS and HSPS 93W-4.9Ni-2.1Fe heavy alloys are dependent on the microstructural parameters such as tungsten grain size and overall homogeneity.